dhcp: dhclient: set type 0 for printable client IDs

The documentation for the ipv4.dhcp-client-id property says:

 If the property is not a hex string it is considered as a
 non-hardware-address client ID and the 'type' field is set to 0.

However, currently we set the client-id without the leading zero byte
in the dhclient configuration and thus dhclient sends the first string
character as type and the remainder as client-id content. Looking
through git history, the dhclient plugin has always behaved this way
even if the intent was clearly that string client-id had to be zero
padded (this is evident by looking at
nm_dhcp_utils_client_id_string_to_bytes()). The internal plugin
instead sends the correct client-id with zero type.

Change the dhclient plugin to honor the documented behavior and add
the leading zero byte when the client-id is a string.

This commit introduces a change in behavior for users that have
dhcp=dhclient and have a plain string (not hexadecimal) set in
ipv4.dhcp-client-id, as NM will send a different client-id possibly
changing the IP address returned by the server.

https://bugzilla.gnome.org/show_bug.cgi?id=793957

1 files changed, 11 insertions, 0 deletions

diff --git a/NEWS b/NEWS
index ede606e5c7..bdb7a45166 100644
--- a/NEWS
+++ b/NEWS
@@ -1,3 +1,14 @@
+=============================================
+NetworkManager-1.?? (not released yet)
+Overview of changes since NetworkManager-1.10
+=============================================
+
+* A non-hexadecimal DHCPv4 client-id is now properly passed to
+  dhclient with the first byte (type) set to zero, as stated in the
+  documentation. This represents a change in behavior since previous
+  versions where the first character of the string was used as
+  type. The internal client is not affected by the change.
+
 ============================================
 NetworkManager-1.10
 Overview of changes since NetworkManager-1.8